Numerous hydrocarbon conversion processes are widely used to alter the structure or properties of hydrocarbon streams. Such processes include isomerization from straight chain paraffinic or olefinic hydrocarbons to more highly branched hydrocarbons, dehydrogenation for producing olefinic or aromatic compounds, reforming to produce aromatics and motor fuels, alkylation to produce commodity chemicals and motor fuels, transalkylation, and others.
Many such processes use catalysts to promote hydrocarbon conversion reactions. These catalysts tend to deactivate for a variety of reasons, including the deposition of carbonaceous material or coke upon the catalyst, sintering or agglomeration or poisoning of catalytic metals on the catalyst, and/or loss of catalytic metal promoters such as halogens. Consequently, these catalysts are typically reactivated in a process called regeneration.
Reactivation can include, for example, removing coke from the catalyst by burning, redispersing catalytic metals such as platinum on the catalyst, oxidizing such catalytic metals, reducing such catalytic metals, replenishing catalytic promoters such as chloride on the catalyst, and drying the catalyst. For example, U.S. Pat. No. 6,153,091 discloses a method for regenerating spent catalyst.
In a some regeneration processes, a catalyst is passed from a reaction zone to a regeneration zone which may include a burn zone, a catalyst heating zone, a chlorination zone, a catalyst drying zone, and a catalyst cooling zone, and wherein the catalyst includes coke; burning off the coke from the catalyst in the burn zone; increasing a temperature of the catalyst in the catalyst heating zone; dispersing the a metal on the catalyst in the chlorination zone, replacing a chloride on the catalyst or both; drying the catalyst in the catalyst drying zone; cooling the catalyst in the catalyst cooling zone.
However, some regeneration processes/systems may require a higher temperature to achieve an optimal desired temperature in the chlorination zone. Therefore, it would be desirable to provide a process which allows for a desired temperature (or range) in the chlorination zone to be achieved.
Additionally, some regeneration processes may require a higher temperature to achieve an optimal drying zone temperature. Therefore, it would be desirable to provide a process which allows for desired temperature in the drying zone to be achieved.
Furthermore, some regeneration processes/systems rely on electric heaters for oxygen supplied to the system. Therefore, it would be desirable to provide a process which allows for the regeneration process to be run with a wider range of catalyst coke values.
Additionally, it would be desirable to provide a process which allows for the proper amount of chlorine to be introduced to disperse the metals on the catalyst, without increasing the amount of chloride on the regenerated catalyst. In other words, it would be desirable to have a process in which the chloride level of the catalyst is decoupled from the chorine used for dispersion so that the process can operate at a lower level of chloride while achieving a sufficient metal dispersion.
Furthermore, some current designs may not allow metal to be dispersed in the chlorination zone or drying zone during some modes of operation. More specifically, in a “black burn” mode the catalyst has high levels of coke and only nitrogen is injected into these two zones. Additionally, no chloride is injected into the regenerator. This operation condition prohibits metal (including platinum) dispersion during the black burn mode resulting in decline in catalyst performance, loss of C5+ yield, hydrogen product yield and low activity.
Furthermore, during other operation modes, coke slippage or slightly higher coked catalyst passing into the chlorination zone, may result in poor metal dispersion, catalyst damage, catalyst fines generation, and equipment fouling. These can shorten the process turnaround interval leading to potential of a unit shutdown resulting in loss of production in the reforming unit. Therefore, it would be desirable for a process in which metal dispersion occurs during various operation modes. It would also be desirable to provide a system which also increases the coke burn to avoid coked catalyst from burning in the chlorination zone.
Therefore, there remains a need for effective and efficient processes for regenerating catalyst.